Kids and cars are a risky combination. While children can normally deal with an hour-long drive from your house to their cousins' house, they struggle to deal with long highway journeys in the car from one state to another. And if you don't want a road trip rebellion on your hands, you have to keep them busy! So, why don't you create a road map for the kids to enjoy in the car?
You can make this out of paper and stick it to the roof of your car, and every so often, they can move the car a little bit closer to the final destination. You'll never hear "Are we there yet?" again!